Method of obtaining aluminum salts from silicates.



aanrn a. mxne'or onono, xanm.

METHOD OF OBTAINING LLUXIKUH SALTS FROM SILIGATES.

Specification of Letters Patent.

Patented Apr. 17, 1917.

1,222,960. Io, Drawing. 'Appllcation filed latch 18, 1818. Serial No. 63, I71.

To all whom it mag concern:

Be it knownthat I, RALPH H. MoKrm, a citizen of the United States, residing at ()rono, in the county of Penobscot and btate of Maine, have invented certain new and useful Improvements in Methods of Obtaining Aluminum Salts from silicates, of which the following is a specification.

It is known that water-soluble potassium salts may be prepared from sericite (potashbearing mica-schist) and silicates of analofous composition, by heating the same with ime or limestoneand salt; or with lime or limestone and salt used in conjunction with a reducing agent. such as a fuel material. (hee'iny )rior U. S. Patent No. 869,011, patented ctober 22, 1907).

Such silicates as are above referred to contain considerable quantities of alumina, which remains with the water-insoluble residue. I have now discovered that this residual alumina is easily extracted by an appropriate acid-treatment, and is t erefore readily recoverable as an aluminum salt, usually a sulfate or chlorid.

In carrying out my process, I prefer to furnace the potash and alumina-bearing silicate. as the hereimbefore mentioned micaschist. with limestone or lime and salt, under conditions which may be as recited in my prior patent above referred to. That is, five parts a v weight. more or less, of the finely powdered schist may be intimately mixed with approximately one part by weight each of limestone and common salt, and the mixture furnaced in a rotary kiln. Suitable furnacing conditions are as disclosed in my said prior patent. although the resent invention is not limited either to tlieproportions of the charge or to the conditions of furnacing as therein described. The liberation of the potassium salt is facilitated by providing reducing conditions throughout the furnacing operation, as for example by the addition of fuel such as coal, oil or gas. The furnaced product is leached with water and the potassium salt recovered in I commercial form by evaporation.

The residue from the water-extraction is now decomposed by an acid reagent, usually sulfuric or hydrochloric acid, whereb the alumina is dissolved as sulfate or orid.

Sulfuric acid is p referably used, since thereby calcium sulfa'e and silica remain undissolved and aluminum sulfate is directly recoverable by evaporation of the solutions as a commercially iure product. Hot strong sulfuric acid (80 70 or above) efl'ects this decomposition in a few minutes. temperatures, or with dilute (15%) acid the same result is accomplished more slowly and not quite so completely. In so far as the decomposition of the residual silicate is con cerned, hydrochloric acid gives similar re-- with the extraction of the potash salts, and

the'potassium and aluminum are recovered, at least in part, in the form of potash alum, which is readily purified by crystallization.

I claim 1. The herein described method of obtaining: commercially pure aluminum salts from silicates-of the sericite type, which consists in furnacing said silicates with lime or limestone and a cl: lorid, producing thereby a water-soluble itassium salt, extracting the soluble potassium salt, and decomposing the residual silicate by an acid reagent.

2. The herein described method of obtaining commercial] y pure aluminum salts from silicates of the sericite type, which consists in furnacing'saf d silicates with lime or limestone, a cblorid and a reducing agent, producing thereby .a water-soluble potassium salt, extracting the soluble tassium' salt, and decomposing the residuanilicate by an acid res nt.

In testimony whereof I afiix my signature in presence of two witnesses.

RALPH H. McKEE.

Witnesses:

Pa'rnrox H. Houunax, F. L. Moms.

At lower 

